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Can subsoil drains remove all moisture to protect road formation?

Water control is essential to enhance subgrade to possess good bearing value and strength. Water movement in soils takes place by the action of gravity and capillary actions. Subsoil drains are commonly placed at least 1m below finished subgrade to maintain a lower groundwater table.


A properly constructed subsoil drain could effectively lower groundwater table and control the capillary rise. However, they may not be able to eradicate completely the upward movement of moisture in soils. Therefore, a sand layer or granular sub-base could be placed on sub-grade to remove and intercept the moisture once it starts to accumulate.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

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Kanwarjot Singh

Kanwarjot Singh is the founder of Civil Engineering Portal, a leading civil engineering website which has been awarded as the best online publication by CIDC. He did his BE civil from Thapar University, Patiala and has been working on this website with his team of Civil Engineers.

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